Research On Key Technologies Of Hybrid Power Quality Compensation Device Based On Multi-winding Transformer

With the increment of nonlinear loads and the randomization and complexity of power system,power quality problems such as lack of var compensation,harmonic current and voltage fluctuation may not only disturb regular production and life,but also lead to massive economic loss.So it's an exigent mission for researchers and power industry practitioners to carry out managing power quality problems to satisfy the demand of customers.Based on the analysis of traditional power quality problems and existing compensation device,key technology of hybrid power quality compensation device based on multi-winding transformer which combines the function of power transmission and power quality compensation is researched in this thesis,main content is listed as follows:1.The topology of power quality compensation device is discussed,along with analyzing the multiple operating mode and different operational principle of the device.The mathematic models of shunt converter based on synchronous rotating coordinate system is established.The topology of series converter is analyzed later,including energy storage link,invert system,coupling mode and filtering link,laying foundation for later research.2.Study of detection technology of current quality problems has been carried out,analyzing ip-iq method based on instantaneous reactive power theory and dq method based on coordinate system.Because of the cross coupling between d and q axis which will make it more difficult for controller design,the complex coefficient vector current controller method is proposed in this thesis by using current ring locus and frequency response,under the circumstance of designing the zero point of the controller which can be offset by the complex pole of the controlled object,so as to achieve the aim of decoupling.By carrying out simulation experiment,the compensation performance of shunt convert is verified,so as to show the advantages of promoting the stability and the robustness of system by adapting the complex coefficient vector current controller.3.Voltage sag detection method and phase locked technique are investigated next.On condition of studying single-phase instantaneous voltage dq detection and single synchronous reference frame software phase locked loop,a SOGI-based fundamental frequency decoupling software phase locked loop is proposed to track the voltage phase of unbalanced voltage and harmonic voltage conditions.The parameters design and root locus analysis of inner current loop in double closed loop are introduced,along with an outer voltage loop controller design based on multiple quasi proportional resonant to compensate the harmonic voltage,meanwhile the compensation performance of series converter is verified by simulation on several conditions.4.On the basis of theory analysis,the experiment platform was manufactured,the design of power circuit and control system are introduced,along with a suite of integrated communication system.Lastly,the compensation effects of the device on several kinds of power quality problems are tested and analyzed to show the validity and rationality of the theory study.